Chemical Formulas from Experimental Data A chemist decomposes samples of several compounds; the masses of their constituent elements are shown below. Calculate the empirical formula for each compound. $$ \begin{array}{l}{\text { a. } 1.245 \text { g } \mathrm{Ni}, 5.381 \mathrm{g} \mathrm{I}} \\ {\text { b. } 2.677 \mathrm{g} \mathrm{Ba}, 3.115 \mathrm{g} \mathrm{Br}} \\ {\text { c. } 2.128 \mathrm{g} \mathrm{Be}, 7.557 \mathrm{g} \mathrm{S}, 15.107 \mathrm{g} \mathrm{O}}\end{array} $$

Molar mass is a fundamental concept in chemistry, representing the mass of one mole of a substance. It's usually measured in grams per mole (g/mol) and can be found by summing the masses of all the atoms in a single molecule of the substance.

For instance, in our example for Compound a, nickel (Ni) has a molar mass of 58.69 g/mol. This means that one mole of nickel atoms weighs 58.69 grams. Understanding molar mass is crucial as it bridges the gap between the mass of a sample and the number of moles, allowing us to carry out moles calculation. Moreover, it touches upon the chemical composition of a compound by reflecting the combined masses of its constituent atoms.

The moles calculation involves determining how many moles are present in a given mass of a substance. The formula for calculating moles is simple: moles = mass (g) / molar mass (g/mol).

In our given problems, this calculation helps us understand the proportion of each element in a compound. For example, to find moles of iodine (I) in Compound a, you divide the mass of iodine by its molar mass, resulting in \( 0.0424 \text{ mol} \). This step is essential for stoichiometry, as it allows for the comparison of quantities of substances involved in chemical reactions.

Chemical composition denotes the identity and quantity of each element within a compound. By knowing the chemical composition, you can describe and understand the properties and behaviors of a substance.

To elucidate chemical composition, it's pertinent to determine the empirical formula, which is the simplest integer ratio of the atoms of the elements in a compound. The empirical formula does not necessarily represent the actual number of atoms present but gives a simplified view of the ratio of each type of atom. As shown in the solutions for each compound, once the moles of each constituent element are identified, it leads to the empirical formula that represents the chemical composition.

Stoichiometry is the quantitative relationship between reactants and products in a chemical reaction. It is based on the conservation of mass and the concept of the mole. With stoichiometry, we can predict how much product will form from a given amount of reactants, or how much of each reactant is needed to create a specific amount of product.

In the context of our problems, stoichiometry is applied when we use moles calculation to establish the ratios that make up the empirical formula of a compound. It's the mathematics behind chemistry, ensuring that the equations balance and adhere to the law of conservation of mass. For Compound c, stoichiometry indicates that the elements combine in a mole ratio of 1:1:4 to form BeSO4, conveying not only the proportion but also giving insight into the reaction stoichiometry of the compound's formation.